The present invention relates to an extrusion molded electrode which is formed as a compound body, in particular for a spark plug for example a ground electrode for spark plug.
The German document DE-OS 31 41 649 discloses a spark plug electrode. It forms a central electrode of the spark plug, or in other words high voltage required for forming an ignition spark is supplied to it. The ignition spark, coming from the central electrode act upon, a so-called ground electrode which is connected with the electrical potential of the chassis of the vehicle. However, it is not limited to this application, but it can also be used for other electrodes as well. The known central electrodes and the ground electrodes disclosed in the above-mentioned literature are produced from metallic initial bodies, for example discs in extrusion process. They have an electrode cross-section profile which approximates the preferably rectangular shape and are provided with a core composed of a first, electrically conductive material and surrounded with a casing of a second, electrically conductive material. During a deformation process, namely the above mentioned extrusion molding, the core is provided with its casing and therefore a cylindrical composite body is produced. The core also has a cylindrical shape which is coaxially surrounded by the casing, so that together the above mentioned cylindrical shape is obtained. In a further working step a flat pressing is utilized and produces a cross-section profile which approximates a rectangular shape. Preferably, the pressing process produces flat upper and lower sides of the electrode and the side surfaces have correspondingly a convex shape. By the flat pressing step, the core assumes a substantially bone-shaped cross-sectional profile. The known electrode has been proven to be satisfactory in practice.